1. Field of the Invention
The present invention relates to a keypad structure and particularly to an electrophoretic display keypad structure.
2. Description of the Prior Art
Electronic products such as cell phones, personal digital assistants (PDAs), and the like usually have keypad keyboards. In present market, keypads are mainly categorized into metallic keypads and plastic keypads. Conventionally, the figures such as digitals, symbols and English letters of the keypads are formed by virtue of printing or laser etching method on the top surface of the keycaps. The figures may be easily stripped off or damaged due to frequently pressing. For this reason, in order to enhance the protection for the figures and increase three-dimensional aesthetic vision as well, it has been developed to form figures on the bottom surface of the keycap components. Usually, for saving area occupied by keypads on the limited surface of the electronic products, a plurality of figures may be formed on each button in accordance with operation modes. Accordingly, users must find a right button to press for performing a desired function in accordance with a selected operation mode through discerning a right figure from a plurality of the figures on a right button among a plurality of figures. Hence, no matter the figures are formed on the top or bottom surface of the keycaps, the figures appeared to users are all of the figures prompting all of the operation modes. Users must make an effort to discern a desired figure among such many figures during operation.
Additionally, an electrophoretic display (EPD) device is usually known to be used in electronic products, such as electronic paper, commercial labels, watches, sports products, healthcare products, and the like, to provide a display screen for users. The electrophoretic display is a reflective-type display device based on influence on an electrophoretic phenomena of charged particles dispersed in a dielectric solvent. A conventional electrophoretic display device includes a glass substrate, a transparent protection film disposed so as to be opposite to and spaced from the glass substrate, and an electrophoretic layer disposed between the glass substrate and the transparent protection film. Conventional electrophoretic display devices may be categorized into passive matrix and active matrix types in accordance with display driver technologies. The electrophoretic display devices are characterized by electric power saving, being light and thin, clear texts and pictures, no problems with viewing angles, being flexible, and variety, and that backlight is not needed.
Japan Pat. Application Publication No. 2008-250259 discloses a keypad using an electrophoretic display, as shown in FIG. 1, which includes a resin film 1, a transparent electrode layer 2, a display layer 3, a spacer 4, a backside electrode layer 5, and a protection layer 6. The display layer 3 includes a plurality of microcapsules 7. The spacer 4 is disposed at the periphery of the display layer 3 and has a thickness the same as or greater than that of the diameter R1 of the microcapsules 7. When the display layer 3 is pressed, the pressure onto the microcapsules 7 can be decreased due to the spacer 4. Accordingly, the microcapsules 7 are not easily broken.
Thus, the microcapsules 7 will be not broken during the insert molding or integral formation. The disclosed keypad has a structure just containing a singular button. In other words, when the electronic product bears a plurality of buttons, a number, which is the same as the number of the buttons, of such keypad structures are needed. Therefore, the cost is relatively high.
Since the keypads of the electronic products have been constantly developed to be relatively thin and small for the devices with reduced size and weight as desired, in addition to aesthetic appearance, functions, and economic aspect, so as to accord with the demand of the market, there is still a need for a novel keypad structure.